1. Technical Field
The present invention relates to a liquid ejection device for ejecting a liquid on an ejection medium that is supported by suction on a medium support unit.
2. Related Art
From the past, inkjet printers (hereafter referred to simply as “printers”) have been put to practical use as liquid ejection devices for ejecting ink as a liquid from a liquid ejection head onto paper as one type of ejection medium in a sheet form that is transported while being supported on a medium support unit, and forming an image containing text or graphics. This type of printer has a plurality of recesses that open at a medium support surface that the medium support unit has, and that are depression formed so as to be separated from the paper supported on that medium support surface, and by suction of the paper by the negative pressure given to these recesses, the paper is supported by suction on the medium support unit.
With this kind of printer, there are cases when so-called “borderless printing” is performed, by which ink is ejected from the liquid ejection head onto the entire surface of the paper to form an image. When performing this kind of “borderless printing,” recesses which accept ink ejected from the liquid ejection head outside of the width direction end parts of the paper are provided such that the paper end parts are positioned inside the openings thereof. Because of that, at the recesses at which ink is ejected, there are opening parts on the medium support surface which are not covered by paper, and due to negative pressure that suctions the paper, there is a flow of air (atmosphere) that is suctioned to the recesses via this opening part.
At this time, due to the air suctioned to the recesses from the top surface (image forming surface) side of the paper, it is possible for flight interference to occur, by which the flight of ink ejected on the paper is curved. In light of that, for example as disclosed in Japanese Laid-Open Patent Application Publication No. 2005-219434, it is proposed to have the recesses and the pressure chamber side be in communication using a flow path of a shape for which the recess (vent hole) opening surface area gradually decreases and then becomes fixed as it faces the pressure chamber side that gives negative pressure for suctioning the paper. By having the pressure chamber and the recesses be in communication in this way, unnecessary ink ejected into the recesses is flowed to the pressure chamber, and also, it is possible to increase the flow path resistance during suction on the pressure chamber side at the recesses, so it is possible to reduce the flow speed of air suctioned to the recesses. As a result, in the liquid ejection area which is the image forming surface side (top surface side) area of the paper on which ink is ejected toward the paper from the liquid ejection head, the constitution is such that the flow speed of the air that flows due to suction is weakened, the flight interference of ejected ink is suppressed, and unnecessary ink is accepted using suction.